Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 6-1 FitzGerald ● Dennis ●...

Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.6-1

FitzGerald ● Dennis ● Durcikova

Prepared by Taylor M. Wells: College of Business Administration, California State University, Sacramento

Chapter 6

Network Design

BUSINESS DATA COMMUNICATIONS &

NETWORKING


Outline

• Network architecture components• Traditional network design• Building-block network design– Needs analysis– Technology design– Cost assessment

• Implications for management


Network Architecture Components

• Local area network (LAN) – Ch. 7• Building backbone network (or distribution layer) – Ch. 8• Campus backbone (or core layer) – Ch. 8• Data center – Ch. 7• Enterprise edge– Wide area network (WAN) – Ch. 9– Internet access – Ch. 10– e-commerce edge – Ch. 7 & 11


Network Architecture Components


Traditional Network Design

• A structured systems analysis and design process• Network analysis phase includes:

– Meeting with users to determine the needs and applications– Estimating data traffic on each part of the network

• During the network design phase, the logical and physical networks are designed and circuits and hardware selected

• Implementation phase is the building and implementing of the network


Traditional Network Design

• Pros– Useful for static and slowly evolving networks

• Cons– Costly– Time consuming– This approach may not be adequate today due to:

• Rapid changes in technology• Escalating network traffic demands• Decrease in hardware costs and increase in staff costs


Building Block Network Design

• Uses a few standard components to simplify design and reduce costs

• Iterative design phases– Needs analysis

• Understand current and future network needs (users and applications)

– Technology design• Examine available technologies to

determine which meet or exceed needs• If needs are difficult to estimate, build

higher capacity

– Cost assessment• Evaluate financial costs of technology


Needs Analysis

• Why is the network needed?– Performance issues may exist– The organization may be standardizing– Hardware may need replacement

• What users and applications must be supported?• Goals differ depending on the network component

– LAN and BN typically are built with organizational ownership and are often built with excess capacity

– WANs rely more on leased equipment and circuits are typically designed at or near capacity with organizations leasing additional circuits as required

Needs Analysis


Needs Analysis

• Baselines– Create metrics of current operations to compare design

requirements against– Baselines may include• Sequence of operations• Processing times• Work volumes• Existing costs• Existing user/management needs

Needs Analysis


Needs Analysis

1. Break down the network into architectural components– Evaluate all seven components– Often easiest to start with WANs– Geographic scope of network

2. Review the existing and expected applications that will use the network– Identify hardware and software requirements for these

applications– Identify protocols used by applications

Needs Analysis


Needs Analysis

3. Identify and assess network users– Some users may have very different needs– How many of each type of user?

4. Categorize network requirements– Mandatory– Desirable– Wish-list

Needs Analysis


Needs Analysis• Deliverable: Logical network design

Needs Analysis


Technology Design

• Development of a physical network design (or set of possible designs)

• Design includes clients, servers, circuits, and networking devices (routers, gateways, access points, switches, etc.)

• What new hardware needs to be purchased?• Can the existing equipment be upgraded?

Technology Design


Technology Design

1. Designing clients and servers– Specify of the devices needed in standard units– “Typical” users are allocated base-level clients– “Advanced” users are allocated advanced clients– Servers are similarly allocated based on application

needs– Definitions of “typical” and “advanced” change as

hardware costs fall, and capabilities increase

Technology Design


Technology Design

2. Designing circuits– Capacity planning is the estimation of circuit size

and type required for each network architecture component

– Circuit loading is an assessment of the amount of data transferred across a circuit (currently or in the future)

Technology Design


Technology Design

• Estimating circuit traffic– Average traffic vs. peak traffic– Designing for peak traffic is ideal

• Estimating message volume– Count messages sent in the current network and multiply by the

expected growth rate

• Precision may not be the major concern– Obtaining precise estimates is difficult and expensive– Standard circuit speeds “stair step”– Traffic typically increases more than anticipated

Technology Design


Technology Design

• Should network designers plan for excess capacity?– Upgrading costs 50-80% more than designing higher capacity

time– Very few complaints about overcapacity

• Most organizations intentionally overbuild• The turnpike effect occurs when traffic increases faster

than forecasts– When networks are efficient and fast, users will use

them more frequently– Most networks designed with excess capacity end up

using overcapacity within 3 years

Technology Design


Technology Design

3. Network Design Tools– Modeling

• Users create diagrams of existing or proposed networks– Discovery

• Some tools can automatically create network diagrams by examining existing network

– Simulation• A mathematical technique used to model the behavior of

a network under real conditions• Simulates applications and users generating traffic and

responding to messages • May highlight potential problems

Technology Design


Technology Design

• Deliverable: One or more physical network designs– Multiple designs may be created to highlight tradeoffs

between performance and cost– Design of circuits and networking devices– Designs for new/upgraded clients and servers

Technology Design


Technology Design Technology Design


Cost AssessmentCost Assessment

• Financial analysis of the various technology design alternatives

• Complex process that requires analysis of many factors:– Circuit costs (cabling and installation)– Internetworking devices (switches and routers)– Hardware costs (clients, servers, power supplies)– Software costs (operating systems, application

software and middleware)– Network management and maintenance costs – Operations costs to run the network– WAN and Internet circuits



• Request for proposal (RFP)– Detailed specification of equipment, software, and services

desired from vendors– Typically used in large network purchases– May include timeline and evaluation criteria for proposals

• Allows the organization to evaluate offerings from different vendors

• Multi-vendor proposals– May provide better performance– May be less expensive– May be more difficult to manage



• Selling the proposal to management– Understand that networks, data centers, and most

information technology is viewed as a cost center– Make a business case by focusing on organizational

needs and strategy– The importance of network speed, reliability, and

security are easy for non-technical users to understand– Avoid focusing on technical details and jargon



• Deliverables– Finalized RFP that is sent to vendors– Revised technology design with detailed specifications

including exact products and costs– Business case for the network design


Implications for Management

• Network design increasingly relies on standardized technologies and a building-block design

• The cost of hardware, software, and circuits is less expensive in the long-run than human resources to manage network– This may make more expensive hardware that is easier

to manage a better long-term financial decision• Network usage continues to grow and designing networks

with extra capacity is less expensive than upgrading later

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